[Bug 1864864] Re: [SRU] pthread_rwlock_trywrlock results in hang

[Steve Langasek]

Hello Ondřej, or anyone else affected,

Accepted glibc into bionic-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/glibc/2.27-3ubuntu1.3
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
bionic to verification-done-bionic. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-bionic. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: glibc (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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https://bugs.launchpad.net/bugs/1864864

Title:
  [SRU] pthread_rwlock_trywrlock results in hang

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Bionic:
  Fix Committed
Status in glibc package in Debian:
  Fix Released

Bug description:
  [Impact]

   * pthread_rwlock_trywrlock and pthread_rwlock_tryrdlock before glibc
  2.30 could hang:
  https://sourceware.org/bugzilla/show_bug.cgi?id=23844#c14

   * We are especially able to reproduce the problem with BIND 9.16.x
  when --with-pthread-rwlock configure option enabled

   * But the impact is not limited to BIND 9.16, but any multithreaded
  application using phtread rwlocks

  [Test Case]

  * Fetch the source program and build it:
  $ wget https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1864864/+attachment/5333068/+files/bug23844.wr.c
  $ gcc bug23844.wr.c -lpthread -o bug23844wr

  * Run the resulting binary a few times. On affected systems, it should
  hang in less then 10 attempts.

  $ ./bug23844rw
  trylock_wr
  500000

  (...)

  $ ./bug23844.wr
  trylock_wr
  <hangs>

  [Regression Potential]

   * The upstream fix has been in glibc 2.30 and later
   * Debian has the fix in 2.28-8 as part of "git-updates.diff" from February 2019

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